As a tobacco filter which removes tars from the tobacco smoke and insures a satisfactory smoking quality, a filter plug prepared by shaping a fiber bundle of cellulose acetate fibers with a plasticizer such as triacetin is generally used. This filter has an adequate pressure drop and satisfactory cross section, and, in this filter, the constituent filaments have been partly fused together by the plasticizer to be shaped, so that the filter has a suitable firmness as required of a filter. By the same reason, however, when such filter is discarded after smoking, it takes a long time for the filter plug to disintegrate itself in the environment, thus adding to the pollution problem.
Meanwhile, a tobacco smoke filter made of a creped paper manufactured from a wood pulp sheet and a tobacco filter made from a regenerated cellulose fiber bundle are also known. Compared with a filter plug comprising a cellulose acetate fiber, these filters are slightly more wet-disintegratable and, thus, of somewhat lower pollution potential. However, in these filters, not only the aroma and palatability of tobacco smoke are sacrificed but also the efficiency of selective elimination of phenols which is essential to tobacco filters can hardly be expected.
Further, according to a conventional technology which comprises creping and/or embossing a sheet-like material and wrapping up the creped and/or embossed material into a rod filter, an adequate pressure drop (puff resistance, such a suitable firmness as not to impart an unpleasant feeling to a smoker and a homogeneity of a cross section can hardly be expected concurrently. By way of example, a firmness of a filter can be enhanced by use of a plasticizer or a specialized binder as in, for instance, a filter made of a cellulose acetate fiber bundle, or by modifying the cross-sectional configuration of a constituent fiber. The pressure drop of such filter may easily be regulated by adjusting depth of crepes or embosses formed by creping or embossing process. However, adjustment of the pressure drop to an adequate range results in coarse structure (tissue) of the filter, so that the firmness of the filter is decreased and cross section of the filter becomes heterogeneous. Therefore, a filter having satisfactory properties can hardly be obtained.